Mining cutter bit having a resilient tongue



Nov. 18, 1958 A; o. BRUESTLE m-Al. 0,

MINING CUTTER BIT HAVING A RESILIENT TONGUE Filed March l5, 1957 IN V EN TORS. 42M! 0- Bazaar/.5 C4400! .3. Kent's: 5e,

ATTORNEYS.

States The invehtion will be describedin. connectionwith cutter bits for mining machinery, it being understood that the principles of the invention are applicable to other structures presenting similar problems.

It is an object ofthe invention (as applied to mining machinery) to provide an improved cutter bit 'of the type which is driven into a socket which willhave greater security of retention without being more diflicult to remove and replace.

It isan object of the invention to provide a cutter bit for use in a tapered socket which insures accurate gauge, i. e. the engagement of the shank to a fixed distance in the socket, while at the same time insuring positive retention of the shank in the socket.

These and-other objects of the invention which will be set forth hereinafter or willbe apparent to one skilled in the art upon reading these specifications are accomplished by that construction and arrangement of parts of which the aforesaid embodiment will now be described. Reference is made to the accompanying drawings, wherein:

Fig. 1' is a side elev'ational view of a cutter bit embodying the invention.

Fig. 2 is an end elevational view thereof. I

Fig. 3 is a view similar to Fig. 1 but illustrating an alternate embodiment of the invention.

Fig. 4 illustrates engagement of the bit of Fig. 1 within a socket.

The invention pertains primarily to one-piece cutter bits and will be so described. However, it is possible to realize the invention in connection with structures in volving a head and shank, the head being adapted for the holding of replaceable cutter bits.

In mining machinery, powered heads or chains are provided with members having recesses-or perforations forming sockets for the rcception of' the shanks of cutter bits or cutter bit holders. The shanks'are held in the socket members in various ways, including the use of set screws. It will be understood that the bits of mining machinery, as well as the heads or chain elements having the socket members, are subjected to very great stresses during the cutting operation, and are. also subjected to excessive vibration. Consequently it becomes necessary to hold the shanks in the sockets in such a way as to withstand the stresses, and also to provide against loosening under the combined effect of stresses and vibration.

Also, it will be understood that the powered heads or chains normally carry a plurality of cutter hits, the cutting points of all of which should be located at such distances from the socket members that each bit will do the desired amount of cutting. This is what is termed gauge. It is necessary in order to attain proper gauge that the shanks of the cutter bits or bit holders enter the sockets to a fixed and accurate distance.

It has hitherto been suggested that the shanks of cutter bits be provided with a taper or shaped as a wedge, and that the recesses or perforations in the socket members be correspondingly tapered. Under these circumstances, the shanks are merely driven into the socket members atent where they are held frictionally, i. e. by the wedging action. When it is desired to change bits, the shanks are knocked loose or pried out of the sockets.

Such structures have, however, involved substantial'difficulties. If the tapers are made too abrupt, the engage.- ment is not sufficiently positive, and" the bit is likely to become dislodged under the stresses and vibrations referred to above. On the other hand, while the firmness of engagement increases as the taperbecomes more gradual, toogradual a tapermakes the gauge uncertain, since the shanks canenter the sockets to varying distances.

It must be remembered also that mining machinery is subjected not only to physical wear but also to the cor.- r'osive action of mine waters, many of whichare acidic. Thus it becomes practically impossible to maintain the accuracy, particularly of the socket members. After a relatively short period of use, the socket members are likely to lose their power to retain tightly even the shanks of new bits.

For these reasons driver-type bits have not given trouble free service. A :bit structure which avoids the above difficulties will now be described.

In Fig. 1 there is shown a one-piece bit (i. e. a cutting bit in which the cutting point, the head, and the shank are integral or permanently joined together). The exemplary structure comprises a head land a shank 2; The head usually has a slight forward extension 1a which carries the cutting' face or point, which may be a specially hardened portion of the bit body. More usually, however, the cutting point is formed from a small block 3' of- Carboloy or otherhard alloy, such as tungsten carbide, inset in a groove in the-bit head and welded thereto. The hard alloy block is' usually tilted forwardly at an angle of about 10" bit. It will be noted that the cutting point is backed by a very substantial depth of metal in the head.

The forward extension of the head provides a downwardly facing shoulder 4 which,.normally lying somewhat above the top surface of the socket member, may be used in prying the bit out of the socket by means of a crowbarlike instrument.

7 In the embodiment of Fig. l, the shank of the cutter bit is providedwith a straight or planar front edge 5 parallel to the major axis of the bit. The rear edge 6 of the bit shank is, however, generally tapered as shown, with respect to the front edge 5, the taper being toward the bottom of the shank. However, as shown, the rear edge 6comprisesv angularly related surfaces 7 and 8 meeting at a vertex 9, the surfaces 7 and 8 thus imparting to the edge 6 an extremely shallow V-shaped form.

' As shown, a slot 10 formed in the shank 2 demarks a tongue 11 comprising the inclined surface 8, the tongue having. a slight flexibility or resilience with respect to therest of the shank. In forming'the tongue, the slot 10 is primarily cut substantially parallel with the surface 7, as indicated by the broken lines 10a, the metal comprising the tongue being thereafter expanded outwardly as shown by the solid line construction. The tongue 11 thus being outwardly and resiliently displaced, coacts to retain securely the bit within a socket, as will presently be more clear.

In general, the bit is usually a steel forging and after attachment of the block 3, the forward and rear faces of the shank are formed, machined or ground to the required parallelism and taper, the original or basic taper of the rear edge being in conformance with. the required taper of the surface 7. Thereafter the slot 10 is cut, the tongue 11 expanded outwardly and the forging hardened. As will be obvious, the depth of the slot 10 defines the position of the vertex 9 above mentioned. For this reason and as will later be more clear, the slot does not to the longitudinal axis of the extend throughout the length of the shank but terminates a substantial distance below the level (indicated by the dotted line 12) of the top of a socket member into which the shank is to be driven.

With reference now to Fig. 4, a suitable'bit holder 13 comprises a socket or perforation 14 having a straight or planar inner front surface 15 and a rear inner planar surface 16, theseinner surfaces of the socket as shown being angularly related in the order of 6 and thus being in conformance with the basic outer contour (the contour previous to outward displacement of the tongue 11) of the shank 2 as above described.

When inserting the bit into the holder 13, the shank 2 (with the tongue 11 in expanded relation) is driven into the perforation by blows delivered onto the head of the bit. Due to the resilience of the tongue 11, it will be depressed inwardly as the bit is driven to its fully inserted relation as shown, the tongue thereafter tending to reexpaud providing firm frictional engagement, serving to retain the parts in position. It will be obvious that the tapered relation of the parts serves to define the required cutting gauge.

The tapered relation of the front and rear surfaces of the shank, and likewise the front and rear'surfaces of the socket, is preferably in the order of 6. This value may be departed from, but the basic taper should not be less than about 3 or more than about or difiiculty is likely to be encountered with lack of gauge accuracy or lack of holding power.

With reference now to the modified embodiment of Fig. 3, the cutting bit here shown comprises a head 20 and a shank 21. In this arrangement the straight front edge 22 of the shank is tapered with respect to the major axis of the bit, the taper here depicted being in the order of 3 with respect to the said major axis. The rear edge 23 of the shank again comprises angularly related surfaces 24 and 25 meeting at a vertex 26, the inclination of the surface 25 being determined by the amount of outward deformation of the tongue 27 again comprising an expanded slot indicated at 28. The tapered relation of the basic surface 23 (before expansion of the slot 28) being in the order of 3 with respect to the major axis of the bit. Thus the basic taper of the shank 21 is again in the order of 6. 7

It will be clear that upon obvious modifications thereof the bit holder 14 (as described in conjunction with the bit of Fig. 1) may readily be adapted to receive and otherwise to properly accommodate the modified bit of Fig. 3 as just described.

It will be clear also that dimensions and proportions of the structures illustrated may be varied, particularly in connection with the nature of the metal of which the shank is made to provide more or less resilience. The

shank is normally rectangular in cross-section, although its corners are-preferably rounded or beveled as generally indicated at 29 throughout the various views of the drawings.

As will further be clear and for purposes of illustration, the outward deformation of the tongues 11 and 27 has been proportionately exaggerated in the drawings. In this regard it has been found that an outward deformation of from 10 to 40 thousandths of an inch is satisfactory for use with .a shank of about one inch in median width. Greater deformations may be used; but the expanded end of the shank should be kept narrow enough to enter the socket.

Due to the resilience of the tongue, the wedging fit will be tight despite minor inaccuracies in the formation either of the bit shank or the socket opening. Moreover, it has been found that the arrangement compensates for normal degrees of wear as well as for normal degrees of corrosion due to acidic mine waters. At the same time the degrees of taper disclosed provide accurate determination of gauge without unduly reducing the required tightness of the wedging action.

Modifications may be made in the invention without departing from the spirit of it. The invention having been described in certain exemplary embodiments, what is claimed as new and is desired to be secured by Letters Patent is:

1. A cutter bit for mining machinery, said cutter bit having a head and an integral elongated shank, said shank having a front edge and a rear edge angularly related to each other to provide a wedge shape, whereby said shank can enter a similarly formed opening in a socket member for a fixed distance as determined by said wedge shape, said shank being characterized by a slot extending inwardly from its outer end, and positioned substantially closer to the rear edge of said shank than to the front edge thereof, said slot demarking a resilient tongue adjacent the rear edge of said shank, said slot extending into said shank a distance substantially less than the length of saidshank which is engageable in said socket member, so that the rearward strains of cutting can be resisted at the outer side of said socket member by the engagement of a rear face of a solid portion of said shank with said socket member and by the engagement of a lower portion of said shank at its front edge with said socket member, which lower portion is substantially non-resilient, the said tongue being slightly displaced with respect to the axis of said shank to provide a binding action in the socket opening thereof.

2. The structure claimed in claim 1 wherein the said wedge shape has a taper of the order of 3 to 10.

3. The structure claimed in claim 2 in which the displacement of said tongue is of the order of 10 to 40 thousandths of an inch.

References Cited in the file of this patent UNITED STATES PATENTS 55,423 Lippincott June 5, 1866 521,557 Shepard June 19, 1894 1,244,785 Sessions Oct. 30, 1917 2,521,089 Phipps Sept. 5, 1950 FOREIGN PATENTS 17,095 Great Britain of 1908 

